A sperm acrosome reaction must occur and the acrosomal enzymes must be active for sperm to penetrate the investment surrounding the ovum and ultimately to fertilize the ova. The acrosome reaction has been morphologically described in many species and has been shown to be induced by physiological fluids such as follicular fluid. However, very little is known about the induction of the acrosome reaction at the molecular level. Further induction of the mammalian acrosome reaction has been shown to be non-species specific, therefore, results obtained from these studies of the mouse acrosome reaction might be extrapolated to other animals including man. In attempting to understand the molecular mechanism of induction of the acrosome reaction, it is proposed to: 1) set up and utilize several criteria for evaluation of induction of the acrosome reaction in the mouse; 2) preliminarily characterize the mouse acrosome reaction inducing activity present in bovine follicular fluid; 3) biochemically fractionate follicular fluid to isolate the acrosome reaction inducing macromolecule(s); 4) physically and chemically characterize the purified acrosome inducing macromolecule(s); 5) study the mechanism of action (presumable enzymatic) of the purified acrosome reaction inducing macromolecule(s) and attempt methods to specifically block their reaction in light of any specific mechanism determined. In addition further study will be made on the mechanism of action of rabbit oviduct fluid trypsin (acrosomal proteinase) inhibitors. Since it has been shown that levels of OFTI appear to be hormonally controlled, being lowest at estrus and greatly increasing often ovulation. This increase of trypsin (acrosomal proteinase) inhibitors after ovulation might partially compensate for any release of the lytic acrosomal contents in the oviduct. Also the ability to specifically inhibit acrosomal proteinase may provide a method for preventing conception.